The present invention relates generally to process control systems, particularly to a process control system for optimizing process parameters for nanocomposite materials, and specifically to sample cells for a nanocomposite material process control system.
Advanced materials, such as polymer nanocomposites, serve as innovative structural elements while offering a host of value-added features and multifunctional properties.
Relatively little attention has been placed on pioneering new process control, sensor and in situ control techniques to enhance observability and controllability of key physiochemical changes that occur over a wide range of time- and length-scales during processing of these new advanced materials. Complexity, practicality and tradition have limited many conventional process control approaches to simple environmental control protocols such as staged environmental conditions (temperature, pressure, mass flow, etc.) based on laborious and time consuming factorial tests and offline validation. This works for many conventional material systems, but for advanced materials where critical properties depend on local structure and the synergistic effects of matrix/nanofiller interfaces, this approach is complicated, inefficient and unproductive.
As described in J. D. Jacobs, “Online Impedance Spectroscopy of Thermoset Nanocomposites for Materials In Situ Process Control,” PhD. Dissertation, Electrical Engineering, University of Cincinnati, Cincinnati, 2009, included as part of provisional application 61/353,704 and fully incorporated by reference into this patent specification, the inventor has developed a computer automated processing system with both integrated impedance spectroscopy sensing and electric field directed morphology. This system is the first to successfully incorporate multi-sensor impedance spectroscopy as an online characterization component in a comprehensive computer automated system for processing nanoclay/epoxy thermosets in a controlled and repeatable process; and, also induce field-aligned morphology of intercalated nanoclay by applied quasi-static electric fields.
This new material process control system establishes a development platform for overcoming common limitations suffered by conventional material processing practices by combining environmental control (computer automated temperature and pressure), online impedance spectroscopy (non-destructive, multi-sensor, multi-length-scale information), and electric-field actuation into one computer controlled system. This approach to material process control, particularly for use with nanocomposites and other advanced material fabrication processes, provides a novel set of powerful tools for sustained, repeatable synthesis and development of next-generation feedback process control methods where online strategies may be a prerequisite for obtaining material products with important value-added or tailored physical/chemical properties. In contrast to conventional processing techniques, electric-field actuation techniques provide a novel means for designing materials, particularly directed morphology of layered silicate/epoxy thermosets) with anisotropic properties.
The ability to perform online impedance/dielectric sensing and characterization during a material processing cycle has a multifold impact.
First, the system provides a rich set of time-dependent information at a continuum of length-scales and frequencies in a non-destructive, non intrusive way by use of embedded and/or surface mountable sensors. The use of impedance spectroscopy as a sensor is a well-known electrical characterization technique capable of probing a wide range of molecular and charge transfer phenomena, which in turn can provide direct, repeatable information regarding the state of cure, interfacial/morphological characteristics, and other important material related properties.
Second, online sensor data facilitates an ability to discover and develop advanced feedback process control strategies useful for optimizing material manufacturing by minimizing cure cycle time, material variability, and establish correlations between online data and desired material properties. This also provides a way to shift labor- and time-intensive QA/QC tasks, typically performed by offline validation measurements, into a “feedback loop” where sensor data can potentially indicate deviations in a real time manner to minimize feedstock waste and processing time; and, where corrective measures may be applied automatically to guide the material processing towards a goal product.
Effective manufacturing of emerging material systems requires the assurance of reproducibility and quality. Reaching goals of simplifying processing cycle optimization, and minimizing batch variability and costs associated with feedstock waste, requires comprehensive monitoring and control using innovative strategies that operate within the boundaries of the process. Therefore, new development opportunities exist for online sensor/control techniques to help identify and realize the full performance potential of a material system.
Two very critical components of any such processing system are the sample mold and sensor cells for holding and instrumenting materials being processed. Typical problems include sample deformation during curing from thermal expansion and air entrapment and bubble formation.
It is, therefore, an object of the present invention to provide new and improved sample cells particularly adapted for use in a nanocomposite material process control system.